3 feet tall in a 4" pot... How are they even standing up? Can you post a pic?

You could always put them in large pots and bring them outdoors during the day time

I start mine on March 28 for May 11 planting. This works great.

They are clustered together (pots almost touching), so they are mutually supported. Some of the leaves and small shoots lean on the bay window.

Yeah, I should have delayed, but my prior experience didn't have them germinate for a month. In the aerogarden, they sprouted in 5 days.

I don't see how you can avoid potting them up if you want to keep them going. I wouldn't prune now. If there's a way to get them outside, at least during the day, go for it. You could try one of those cheap plastic greenhouse/shelving unit things.
Alternatively, you could call this first batch a trial run and either give them away to someone who has a home for them or let them be and have a first-hand experiment on root-bound tomato plants. You've time to start another batch of seeds given the rate at which this lot germinated.

Agree that if you want to keep them alive you will have to pot them up to larger containers, likely 2x in a month. The alternative is to take cuttings from them to root. Those rooted cutting will be the plants you will put in the garden and toss these mother plants. Instructions on how to do this are available on the Tomato forum here.

The odds of these plants survival while remaining healthy, for another month, and then surviving hardening off and then transplanting are slim.

Dave

I would definitely start a few fresh ones right now whatever you do... it is not too late.

Personally, I would pot them up into gallons, burying as much stem as possible; get them hardening, then look into season extenders. I use water walls, planting mine in mid-late April in zone 5b (though those only help when the plant is below the top, so you'd have to dig in deep or trench most of the stem). I don't quite understand waiting until May for zone 7--mine is May 12. Of course, it's wacky weather this year for some places. It may be more trouble than starting new seeds or cuttings.

I would take a healthy not too long sucker from each plant, and stick it in a pot. Trash the parent plant and keep the suckers. And if you're in zone 7, surely you can plant them out before May.

what variety is this to grow that tall this quick? I would put together a low tunnel and put them in and would also cut off suckers to start new plants. I always plant bush type determinates for my early plantings. they won't get much over3' at harvest time.

I had such problem my first year growing tomatoes. Actually, I left for three days and come back to them all laying on their side. I was devastated and thought of throwing them all away. But got an advice - to buy 2 gallon pots, soil, take the bottom leaves and all shooters away and plant them in a big pot laying down their stems in spiral in the pot the way only about a foot is above the soil soil. There was nothing to loose(other than money, ha-ha)) and I did it. The most challenge was to plant them later outside with a such root ball, but they grew so many roots, that the root ball stayed together. Just do not water for few days before setting them outside to have them almost dry for replanting. It will make it lighter and easy to work with. I still needed second person help to hold the greens, while I am taking roots with both hands. It was great tomato crop that year).

Lots of good advice here. You can make a quick high-profile greenhouse by turning a table upside-down and securing sheet plastic over the legs. Be sure to vent.