The N920 has no keyboard and that is why Maemo 6 will be on it (Touch centric OS).
Maemo 5 is already very touch-centric, almost everything can be done with a finger. It has both a HK and a VK. Maemo 6 will just take it a little farther, to the point only a VK is required for everything.
I still wonder if 5 and 6 will be blended together or is 6 replacing 5?
OS upgrades are almost always 'blended'. Windows Vista is 'blended' with Windows 7. Maemo 6 will 'replace' 5, but only as a next step, an update, not a totally new OS. Maemo is basically just a Linux distro highly optimized for mobile phones and will go through generational changes like any other distro or OS.
...if I am not worried about the N900 being supersede within a few months, you should not be worried
Me either. The N900 will get OTA updates such as Flash 10 and more portrait mode stuff, and could get some (many?) features from Maemo 6 backported to it. If so, good. If not, it won't stop working or become worse than it was. It'll continue to be a very good unit with Maemo 5.
Devs insist it (N920) will be capacitive though.
This appears to be likely, but nothing definitive has been said AFAIK. It could still be resistive. There is some possibility of it using a new combo resistive/capacitive screen.
I think the G1 display is a little too sensitive, so a little less is good for me. Plus you have more options with resistive (stylus, finger with or without glove). A very sensitive resistive display seems a better option to me.
Agree completely. A really good resistive should be like the best of both worlds.