Ask the hotels
When I was staying at the Westin Khao Lak, someone asked how many SPG points it cost for a night there. The front desk attendant said 2k but it will be 3k in February. So, the hotels know. If you're interested in staying at a property, you could call the hotel directly to see if they are able to share with you whether or not their hotel will creep up a category. Obviously, I would agree, it would be better if SPG told us, but this is a backdoor way to find out...