ZX is really more like Zero. Despite taking place hundreds of years after the Zero series (I believe Classic, X, and Zero series are each about a hundred years apart), ZX is similar in gameplay, and also has Zero references, but it's a lot less apocalyptic.
I haven't seen much of Star Force but it seems too similar to the Battle Network series. Therefore, I'm hesitant to call ZX and Star Force two new Mega Man "series" yet.
Remember when people joked that Capcom couldn't count to 3 because of the seemingly countless Street Fighter IIs? Now it's like they can't count to 9 because both MM (Classic) and MMX have stopped at 8.
(If anyone thinks Mega Man X means Mega Man 10, they deserve a charged Mega Buster to the crotch. I'm surprised that even Penny Arcade made that error.)
Last I counted, there are over 60 Mega Man games among the various series (not counting Mega Man cameos in other games). Capcom themselves have claimed to have over 100, but I'm not sure how they got that high, even if they probably count remakes as more than one (like Mega Man & Bass on the Super Famicom and GBA as two separate ones), and maybe they are also counting some cameos. At over 60 games in just under 20 years, that means on average there's a new Mega Man game every few months, but it doesn't ever seem that way since they'll probably do something like release two versions of the next Battle Network game each year like they have for the past few years. They'll get to Battle Network 8 soon enough, in a year or two, and then what? That's okay, if Capcom's phobic about the number 9 they could continue Zero, XZ, Star Force, or *gasp* Legends...
For the record, I really liked Mega Man X: Command Mission (an RPG in a platforming series) and Mega Man: Network Transmission (a platformer in an RPG series). People complain about Mega Man getting stale but then they don't even play the games where they mix it up. Hypocrites.