Work in progress. Fremantle and Harmattan will probably make us see Diablo as we see Bora and Mistral today.
We are commited to http://wiki.maemo.org/Objective:Maemo_variants
Investing more resources having Fremantle fixes available also for Diablo might look like a more sustainable approach but... what if investing heavily in the future releases is actually the best way for Maemo to become really sustainable?
There is not such 'planning early obsoletion'. If you think device manufacturers make better business through obsoletion than through user satisfaction and customer retention, think twice. This sector is simply running fast, very fast. Look around. Not being fast is not very sustainable and to be fast you need to set priorities and make compromises.