According to the most commonly referenced trade chart, pick 12 is worth 1200 points and pick 22 is worth 780 points, so those two picks combined gives us 1980 points to deal away, while pick 4 is worth 1800 points. Later picks are worth even less. So trading our two firsts for pick 4 would be a more than fair offer. Offering the same thing for pick 5 is generous, for 6 is really generous. Of course, if somebody else offers 2000 points worth of stuff to move up, then that is the true market value for that pick, and the trade chart means bupkus.
I am perfectly content with giving up our two firsts this year, or a first and a second, to get a QB that the front office really likes. I see no reason to even consider adding in next year's first rounder unless we are trying to move to #2 or #1, and even then, I'd say that is way too much to give up. So for me, next year's first round pick is basically untouchable.
If QB's go 1-2-3, then it probably doesn't make sense to trade up much unless we are convinced that the fourth QB still remaining is really better than one of the first 3 taken.
For me, pick 4 from Cleveland, or 5 from Denver, or 6 from Indy, or 7 from TB - I'd be very happy to give fair market value or even a little more than fair to get the QB we want at any of those spots. And I think all of those teams would at least listen to an offer that was better than fair market value according to the trade chart.