Do Marriott hotels make more rooms available - sometimes, but, no gaurentees on that, it is decided by the individual hotel and I haven't noticed threads discussing this being anything as noticable as airline management (Marriotts seem to provide in advance, so in general there would only be availability a few weeks before if the hotel has loads of rooms spare they might try to get some points for)

Will the new program change it? Yes - you should be able to find availability on January 15th

If you are forced to stay during this specific week I'd recommend you wait until the 15th January 2009 and then make a booking straight away - it will cost you more points but there should be rooms available.