Originally Posted by SkyExplorerYYZ

If you reach 50k status, you only need 25k more miles to reach 75k, as well as the applicable SQDs. But as others have said, you need to qualify by the end of the year.

But one thing worth pointing out which may not apply for you is that this only does NOT work like this for promotions that give status. For example, if you earn 25k status through credit card spend (100,000 EDQs), in order to reach the 35k status you would need to also get 35k SQMs. In that case you don't just need the difference.