Platinum under the merged program which goes into effect on Aug 18, or platinum under the current program? The current gold level will be called platinum under the new program.

Assuming that you mean the current platinum (which will be called platinum premier): the benefits for (current) gold are almost the same as those for (current) platinum, so you might consider doing a gold challenge instead - that way, you start getting the benefits sooner. Then in 12 months, you can do a challenge for the next level (assuming they offer that with the new program). I am a hilton diamond (25 days away from lifetime, which I will hit before the year ends, woohoo!) and did just that back in January, as I was gathering Marriott points for a Maui trip (leaving next week!)

I've found that I get treated very well as a (current program) gold. And who knows what the challenges will look like under the new program... Might be better to take advantage of it now.

Here's the comparison chart for the merged program:
https://members.marriott.com/benefits/