I'm in the same pickle as you. My GPA is rather high (3.9+), so doing well this term won't help me out that much, but screwing up one class will drop my gpa. That being said, I'm not doing so well in one of my classes right now, and since grades won't come out till late June anyway, I'm just gonna go ahead and submit my app before then. I have 8 solid quarters of school completed, so I'm pretty sure it's safe to extrapolate and say I'll do pretty well during my 9th quarter. However, I have emailed some schools and asked if it is OK to submit my app early and then update them later with grades. Most of them said yes, some said "we don't really care about your spring grades that much," so it's a variable response. I'd say go ahead and submit now, then email your schools when your grades come out to see if they want you to update them.
