Seeing as how they just completed rebanding the analog system I wouldn't expect to see a wholesale transition to the 700 P25 system for at least another 1-2 years. Pasadena could presumably pony up their own money for a 700 P25 transition whenever they want since they're a "system partner" (they owned their own independent systems at one time but merged with the county in 2005.) The best heads-up for that would be budget discussions for "radio system upgrades" in the City Council meetings. Furthermore, don't be surprised if Pasadena PD encrypts most or all of their radio traffic when the transition eventually comes.
Since you live in the Stink you should probably subscribe to the
Houston Scan Yahoo group. Updates and info for the greater Houston area are a little more timely there than on Radio Reference.