I dont know how many people really care about their phone being Open, but I can bet they are not even the majority of folks who purchased n900. Open source zealots, please get off your high horses, and smell the coffee. There are far too many great close sourced alternatives in the market. A phone/OS without close sourced apps is a zombie. Look at the great linux. Two critical pieces are close sourced. Skype and Flash, without which the only linux desktop users are left would be RMS himself. And for a much more consumer driven device like a phone, the key for its success is app. As long as you have great apps for the platform, few people care about it being 'open source' or 'close source'.
When they introduced the N770 wasn't it part of Nokia's long-term strategy to eventually add phone features to it? I sure hope that it didn't come about because some bright spark woke up in the morning and suddenly had a flash of inspiration and thought "well we got the N810 and we make phones, how about adding phone capabilities to the N810 and call it the N900?" Seriously, if they can overcome the objections of the beancounters (or whoever decides these things) to fund, develop and market the N770/N800/N810 then how hard would it be to do the same for the N900 which, you know, contains a phone, and phones are supposedly one of Nokia's core competencies and a major source of income.