You Can Do a Ribbon Master in 5 and a Half Months
Yes, you.
I keep seeing posts about people giving up on their RMs popping up on my feed in the wake of the Bank news, so I went back and checked the dates on old messages/screenshots from when I did my ribbon masters. I started in late April and finished in mid-December. That's more than 5 and a half months, but I was doing six ribbon masters at once
Working out the time for one wouldn't be as simple as dividing by six, since there's some up-front, set-up-y stuff that gets done regardless and some things you do in batches, but it'd definitely be much quicker. They were also all coming from the Gamecube, having never done any before (so I was building all battle tower teams, farming berries, etc. totally from scratch), and I didn't even have saves for XD, gen 5, or gen 7. I also was not Pokemonning full-time during that period; in June I moved to another country, and in September I started my final year of uni.
There is no one single definitive amount of time it takes to do a ribbon master; sure, I just rattled off a bunch of factors slowing me down but there was also plenty working in my favour, and there are lots of aspects that will just vary person-to-person.
My point is just that if you start now, it's totally feasible to have a RM make it to the Switch by the end of February. If your sole reason for giving up is thinking you can't do it by then, or the amount of ribbons you need to get feeling overwhelming, just go for it. It's not as hard or as slow as it seems, and you speed up a lot as you go (not only is each successive gen generally quicker than the last, a lot of the experience is transferable - eg. getting better at one battle tower makes you better at the others). And worst case scenario, you don't get everything in time, you probably still have fun and grow more attached to your mons doing it.
Good luck!