Like Tom says, there are no known plans for them to change anything because that is not where Axiom feels that they need to be focused, meaning that it isn't a bad speaker like some others would tell you (thanks Sirquack, I was thinking the same point of reference)...
A couple of years ago, the Axiom subwoofer line was lacking. Not that their products didn't work, or work well, but that they didn't have a piece of the market, mainly the larger, more powerful sub lines... Well, guess what, they came out with several new subs to fill that missing market segment. They've since added the architectual line, outdoor speakers, computer speakers, and have new amps coming out soon, etc... They are making some great steps forward, and filled in the gaps that they had... With no rumor of a new line of center channels, and with a lot of very happy customers with the VP150 (myself included), I don't know why people continue to say that it is lacking or needs to be updated.
Take a look at the VP150 freq. response graph... It looks pretty good to me...
Paradigm isn't a bad speaker. My brother-in-law has some, and he likes them. They are in the lower side of their line, but work well for him.
I tried to look up frequency graphs for the Paradigm centers that you talked about, but couldn't easily find them for comparison. I figured that could help to use some factual data to compare the two and not the word of others who potentially haven't heard the speaker. I wouldn't rip on another speaker product without having first hand experience or without using factual data... It is just frustrating how many people who have never heard Axiom speakers (or claim that they have but really didn't, or listened to them uncalibrated) like to bash them. Actually, strike that... The last time I was over at AVS (for example) and was looking at the Axiom bashers, it wasn't that many people. They just were very vocal about it.