With HTC Sense 3.0, HTC (unfortunately) placed hardware restrictions on it – your smartphone must have a dual-core processor before this version of their souped up user interface is able to run. I would suppose they have learned from this as XDA China claims that older HTC handsets (and those with just one core inside) can run HTC Sense 3.5.
While it is speculated that it will feature a similar unlocking system that is found in Sense 3.0, it will most likely also display additional information for weather as well as messages compared to before.