Thanks for the replies so far! I hadn't considered aiming for SE this year, and once upon a time I would have been keen for mileage runs to achieve status.
But now, not so much, and especially this year. (It's been brutal - and expensive.) I should have been clearer that my priorities are:
1) Maintaining a status (and getting benefits) that are greater than what I get through my Amex Aeroplan Reserve card - at least into 2024, when I expect to reduce my work hours and be able to travel more for leisure. 2022 is going to be about travelling to see family in the aftermath of the health crises of 2021-2022. There will be some travel for fun in 2023, and hopefully more in 2024.
2) Finding the $ sweet spot between buying cash fares (to build SQD and SQM) and saving money through reward seats (and benefiting from Priority Rewards and eUpgrades.
So, I think it's really a question of whether 75K is significantly better than 50K, such that it would worth spending $ to get to 75K this year. Undoubtedly SE would be better than 50K but I don't think I'll really be in a position to get a lot of benefit from SE in 2022-2023, so wouldn't it be better to roll over SQM in excess of 50K to 2022?