The first was a complete story arch. I don't know they could do a second one without it sucking wind, but I've been surprised before (Toy Story II, Shrek II), but more than likely it will be terrible, akin to Grease II.
Thought to movie was great and there still a wealth of material yet to be drawn from. I would definently want to see a sequel. Especially if it is in lieu of 'Beverly Hills Chihuahua 2' or 'G-Force 2'. ::shudders::
"If we cut the budget are you going to be the one standing at the exit explaining to guests why the ride they just rode is a piece of crap?" - - John Lasseter