What's a realistic goal to improve speed?

I am 52F. I spent the last 6 months working towards a 5k swim, and now that's completed I feel like I need another goal to keep me motivated. I would like to improve my speed, both over a single 100m and my "forever speed" (where it is boredom not tiredness that stop me). Currently these are 1:50 for 100m and 2:02 for forever. the forever speed has been kind of stuck there for a while, and the 100m speed has improved a couple of seconds recently. I'd really like to get these to 1:40 and 1:55 by the end of the year. Do these seem realistic?