If you have LTP in either program as of the merge of the programs (slated for 8/18), then your status should move to MPG LTPP. If it will take merging your accounts to reach 750/10, then that is stated as happening after Jan 1, and your status until then will depend upon what you have now either in the highest of the two, or the result of merging your accounts, so you can go from LT? (depending upon current status) to MPG PP (with your current LT status) to MPG LTPP after the end of the year. This gives members until the end of the year to complete any planned status runs under legacy rules.

If you post your current status in the two programs a more specific answer can be given. For example, I am currently LTG in both programs with 740 and 494 LT nights. I expect to be MPG LTG in both accounts and after I merge my accounts. However, I expect to be MPG LTPP come January.