The answer is no
Well, looks like my ME3 playthrough is going on hold for a bit and my ME2 Replay is coming sooner than I thought. -Mister Warsaw
-- You can change who you romanced at anytime by breaking up with your current partner and then initiating the relationship with the new one (unless you've already broken up with Tali once). ME3 import flags whatever the current romance is as the one which occurred.
You can always use a save editor to set the Tali romance flag and then import that save.
I'm on the 360 so a save editor wouldn't be available. -Mister Warsaw
You can still edit the romance on 360 if you have a save near the end. I don't remember exactly how but you can reset all your romances aside from Tali so that you can reflect any of the main romantic partners possible in ME2.