Are you still able to buy the same brand/style cabinets? If so, without seeing your layout, it seems like you might be able to rearrange things and fill in with new cabinets as necessary. Is your KD independent or affiliated with a particular cabinet line that she's trying to sell you. I suggest you post your layout here and see if people on this forum can help you with your layout.

A friend just did a minor remodel and had 20 year old cabinets. She moved some around and added some in the same style but a darker stain. It looks great.

What brand are yours?

We re-configured some of our cabinets, and had some new ones made. We were stripping and re-staining them, so the finish was going to be the same as long as we used the same wood for the new items. We had a local custom cabinetmaker build the new ones and do the modifications on the old ones. If your cabinets are not too complicated, maybe someone in your area can do the same for you.

We haven't been able to figure out what brand the cabinets are--but they are hickory and the KD said that hickory deepens in color with age so that if we ordered the same cabinets they would not match (not be the rich warm shade yet) and would look strange. Stripping them and restaining them to match new cabinets would be a great idea--but it sounds like a lot of work. I will look into Kitchen Tuneup!

Some additional options to explore- induction cooktops starting with a 1k unit from Ikea with an oven below. This gives you usable counter space when not in use. Or a slide-in like the Electrolux or GE unit.

I wanted to just fill-in with new cabinets in a similar finish, but was told that it will never match the existing cabinets and that we will always be able to tell.

How radical of a change to you want to do? That is, would it require a lot of new cabinetry?

If your remodel is such that your perimeter cabinets will be roughly the same linear footage, just differently configured, then you could do a contrasting island and have enough cabinetry to do all your existing hickory on the perimeter. Even if you don't have quite enough cabs to do the full perimeter, you might be able to set off a section in a contrasting color depending on the floor plan (e.g., if there is a hutch-like area, perhaps).

Can you post a layout of what you currently have and what you'd roughly envision moving to? Then we can give you some more specific ideas.

It sounds like your KD is more interested in selling all new cabinets. Can't say I blame him/her; you can't really expect them to do a free consult on a total redesign and only end up with a cabinet or two as a new sale. It might be that a self-design and a contractor is your better option. Hard to know without the layout though.

We also reused our old cabinets, stripped them, rebuilt some of them, and had some made. It's not perfect by a long shot, but I still have well-built cabinets that I couldn't afford to buy new right now. More importantly, my kitchen is soooo much more functional. I too needed to change things to vent to outside.

I agree that hickory's tone deepen as it ages, and I agree that it wouldn't match initially, I am not sure I agree that it would never match. Usually wood darkens with time and UV exposure. You can expose the new cabinets to full sunlight, using full spectrum lights, to hasten the aging process. My friend did this when her wood floor needed to be patched, you could barely tell after a few months.
Also depending on how/where you put the new additional cabinetry, you could consider doing them in an accent color. I am not really visualizing what you want to do, but lots of people have either the sink or the stove in a different finish. Here are some images I was able to quickly find to illustrate what I mean. When you mix cabinetry colors and finishes purposefully, it looks great IMHO

[Traditional Kitchen design[(https://www.houzz.com/photos/traditional-kitchen-ideas-phbr1-bp~t_709~s_2107) by Seattle Kitchen And Bath Warmington & North

[Traditional Kitchen design[(https://www.houzz.com/photos/traditional-kitchen-ideas-phbr1-bp~t_709~s_2107) by Atlanta Furniture And Accessories The Furniture Guild

[Traditional Kitchen design[(https://www.houzz.com/photos/traditional-kitchen-ideas-phbr1-bp~t_709~s_2107) by Other Metro Interior Designer Kimberly Arnold Fletcher

"the KD said that hickory deepens in color with age so that if we ordered the same cabinets they would not match (not be the rich warm shade yet) and would look strange

Only for a short time. The new ones will darken to match the older ones.

Check with custom cabinet makers about making the infill cabinets you need, because if the idea of waiting for the cabinets to darken naturally isn't attractive, they can easily stain the new stuff to blend into the older stuff.

I had new doors made for my parents kitchen while they were gone for a long vacation, and the cabinetmaker matched the "mid range" tones of age-darkened birch with his stain. The color blending was so good my mom had been home for a couple of days before she spotted the new doors.

Sure it can be done, I would look for a talented finish carpenter, and or custom cabinet shop to do the changes and additions. I'm going to be starting the same type of retro fitting my 26 year old cabinets soon, because many of todays appliances don't fit the same cut outs as in 1986, and I'll be swapping out doors for drawers etc...