Why do people insist that they think they know what Bioware will do? I've played plenty of RPGs which consisted of WAY more recruitable characters with the same level of depth and detail as Mass Effect, so what makes you think Bioware can't do it? Besides, ME2's squad is up to 11 (12 once Kasumi appears), each with their own unique level of depth and personality, upping the number to 13-15 or so (possibly, I'm just speculating since that's a safe-sounding range) couldn't be
that difficult.
Also, they have absolutely NO reason to sideline people for the finale. It's the last hand, all bets are off, no-holds-barred, everything out on the table. They would NEVER get us this emotionally involved with our squad and then suddenly shove them off a cliff and into obscurity by making them cameos or what not, especially since over half the ME2 squad consists of potential LIs.
Now, I can see them making you decide between certain party members (for example, you don't need Liara
and Samara, likely you'll have to pick one or the other, Grunt/Wrex is another instance possibly) However, that doesn't mean there won't be new characters either. Also, I believe in an interview Casey or one of the other devs mentioned how people dying in your squad could result in "consequences". So for instance, if Tali died during the suicide mission, convincing the Migrant Fleet to help you would become MUCH more difficult.
Just like there are incentives to makes certain choices in ME1, there are likely going to be incentives in ME3 for making certain choices in ME2. But Bioware has had ME3 in development
since they started ME2, since they have to think about how the choices made in 2 will impact 3, so it's not like they're rushed for time or a deadline.
