I will collect baseball cards whether they're put out by Topps, Upper Deck, Fleer, Donruss, Pixar, Kellogg's, my neighbor, whoever - as long as they're worth collecting and collecting them provides me with some sort of enjoyment. I'm a glass half full kind of guy, and I really don't think Topps' lack of competition will cause them to release a half-baked 2010 set. On the contrary, I would hope Topps realizes the opportunity it has in front of it, and the company releases some amazing 2010 sets. (After all, that Michael Eisner guy, who is now running Topps, seems to have had a little bit of success in his previous life.)
Upper Deck was innovative and fresh in the late '80s/early '90s, but the product they've released over the past few years pales in comparison to what Topps has released, in my humble opinion. We decided to collect the 2009 Upper Deck base set, and I'm still upset that Series 2 is basically a repeat of Series 1. Short prints and the occasional gimmick cards aside, Topps seems to have struck gold with their Heritage and Allen & Ginter sets. Their 2009 base set is a huge upgrade over the poorly-received 2008 base set, and it makes me wish for a time machine to stop past-Jim from buying those boxes of 2009 Upper Deck in the spring.
I'll conclude by borrowing a quote from Dan's much more eloquent post on the topic over in The Other World, "As collectors, we adjust and buy what we like and that will not change."
UPDATE - I just re-read this post. To clarify, it would depend on which of my neighbors put out a baseball card set as to whether or not I'd collect it. Frankly, some of my neighbors are a little sketchy.