I am in zone 7 also and I started most--but not all--of my seeds months ago. The short answer is "probably" too late for starting seeds. Even with those temps (I am jealous), the shortening days make a difference, but they might overwinter and start growing again in spring if they survive winter. I would absolutely look for transplants though--do you have a garden center or farmers' market where you could buy lettuce, kale/collard, arugula, spinach, etc. seedlings? The Asian green tat soi and the salad green called mache are both particularly cold hardy.
It also makes a difference if you use season extending materials like row cover or plastic. It is pretty amazing what you can grow over winter with some protection.

Check your soil temps. If, like mine, they are still in the sixties then yes the soil is still plenty warm enough for planting. We just seeded several different kinds of lettuce, spinach and chard this week.

But you will have to put them under some sort of cover eventually. Look into low grow tunnels. We have the hoops set up on the rows as we plant and then we can just throw on the row cover as needed.

Dave

i'm planting arugula, lettuce, mustard, kale, tatsoi, mache, and probably a few others today in central virginia... they will be covered eventually but no time soon (i hope)... i'll probably start one more batch in a cold frame in a couple of weeks although i find that the stuff planted after the first week of november tends to grow super slowly moreso from short daylight than temperature imo...

In all my fall planting, I somehow forgot to sow lettuce. I sowed it in some pots yesterday in the hopes that that soil will stay warm longer. I can cover them if it gets really cold too. What have we got to lose? A bit of time and a few seed? I'd try. You're bound to learn something valuable.