if you look at the little webcam image on weather.digsys.bg you can see there is a little fresh snow since yesterday, says that's it's snowing now, but I wouldn't trust their piste reports, they always say conditions are "excellent" which clearly isn't true, but with any luck it should be ok, all the weather sites are forecasting around 20cm of snow over the next few days, I go out on Saturday - woohooo!
If you look at the web cam you can see it is smowing right now. Don't worry, i've been to Borovets 5 times now (going again on 31st) and have always been able to ski.
I got back on Saturday and on the Friday it had started to snow - mid week the lower slopes were getting a bit slushy but if you go up the gondola to the middle station (as it wasn't going to the top) the slopes there were really good and very quiet !