I have kept my my older android phone (HTC Aria) for a backup in case my current phone breaks or I just want to switch back to using Android.  I have also switched over to Tmobile so Im not sure if I will be stuck with a phone that I wont be able to get security updates/patches or newer versions of the OS.  Am I stuck ?

[update]
Just went into the settings and realized that since it was on ATT with this phone, the system update is controlled by ATT.

Looks like Cyanogen Mod supports it

Only up to GB but that's still better than what it has

carrier unless you root it and install your own

what's really funny is that AT&T disabled the ability to install from unknown sources on mine. at one point it had been able to be enabled and then at some point they removed it. Then the manufacturer released a security patch and AT&T sent one of those free texts with a link to install it, but it couldn't be installed because of their stupidity.
I rooted mine after that but didn't change the OS version, just did the security patch, updated the amazon app store app, and uninstalled some ATT bloatware that came built in