As a user I'd like both a general hardware and software(including support) roadmap(s). As a consumer, I'd like to know what is upcoming, so I can make a decision to wait or move on. I'm sure that developers would benefit as well. Something along these lines:

Phone device, Fremantle, no supported upgrade path to Harmatten.(potential community support)
Tablet device, Fremantle, same as phone
1yr+, upgraded phone, Fremantle, Harmatten compatible.
Upgraded tablet, Harmatten
Lower end phone, Harmatten

As a user/consumer, I'd like to see what formats wiil be available and what I can expect in terms of official support. I expect my $ phone to have limited/no support, and get a new one every couple years. If a company wants me to buy a $$$ phone, I expect good support for at least two years, as I will likely keep it longer than that.

Given the confusion here concerning how well Nokia supported the tablets, I'd hesitate to buy a Nokia product (phone-tablet) without a clearer idea of what/how Nokia expects to support it.