You don't need to pot up. That won't make much difference if it is only for 4 days. Just be sure to loosen up some of the roots while planting so they won't continue to grow in circles. Once loosened, they will be able to spread.
Kim

Here is a link that might be useful: My garden

Not sure why you didn't continue this discussion in the other thread...

If you're planning on planting these into the ground where they will get hours of full sun before they're hardened off, they most likely won't make it.

Why don't you pot them up into larger containers, harden them off and plant them out a while later?

I wouldn't bother transplanting them if you are putting them in the ground in 4 days. Are you sure they're root bound? Anyway, as Kim said, just loosen the roots a bit when you plant out and lay it on its side a bit to bury some of the stem so new roots form.

I deliberately grow my seedlings rootbound and here's why.

I transplant from the seed pans when they are about one inch tall or have their first true leaves, to plastic cells about 2 by 2 inches, 4 cells to a unit and 8 units to a standard nursery tray.

And they are grown to outside planting size of 6-9 inches before hardening off and setting out.

I never pot up b'c that encourages a fibrous root system which is fragile and often breaks apart when the plants are set in the ground.

Rootbound plants, sometimes I untangle those roots but it's not necessary, are not fragile, transplant well and adapt very quickly and send out new roots ASAP.

Carolyn

Can they survive? Sure. Just make sure they are well hardened off before transplanting or if you have a way of shading and protecting them in the garden then plant them now.

Dave

Absolutely. See below for a rather extreme example. This plant will be just fine although it is not appreciating the cold/wet weather this week. Tomatoes are very resilient plants.
http://worldtomatoes.blogspot.com/2012/05/planting-day-1.html