Yes ... don't lose heart. You can definitely hold on to some speed with weight training. You can also mix up your runs. Do a couple of intentionall slow/easy runs per week. Use one day for "speedwork" -- whatever that looks like for you. You could do fartleks, short quarter-mile speed intervals, or one of my favorites ... run along to a high-tempo playlist and just let the music carry you.
If you do races, challenge yourself do place a little higher each time in your 50s age group. Or challenge yourself to slice off 5 seconds per mile from the last race you did.
Hang in there!