I started with FZ1. Then bought canon 10D. Also have FZ5. For action shots, dSLR really helps but camera is just one thing, you need to look at the lens also. Also is the action going to be inside or outside? For outside f5.6 is no problem. Most of my bird shots are at around f8 at ISO200 or ISO400 and they much better than what I can get from FZ5. ISO400 on XT/20D is much cleaner than starting ISO on FZ10 (IMHO, others might disagree).
I use 100-400L IS and 400 f5.6 prime lens. My low light lens is cheap 50mm f1.8. For inside stuff, you need f1.8, atleast f2.8. Don't expect to get reach of fz10 at f2.8 at cheap price, 300mm f2.8 and 400 f2.8 are quite expensive and heavy.