This changes the LSA landscape quite a bit. Until this point, LSAs were the domain of mostly foreign manufacturers, the largest of which is on pace for selling ~200 airframes this year.
Cessna brings to the mix a reputation for sturdy, easy to fly airplanes and financial stability that no other LSA maker has. The reputation will, at least initially, lead to more widespread acceptance of LSA. Even now, most pilots give LSA a snicker and the cold shoulder, although that is changing slowly. The financial stability will allow them to (hopefully) get the manufacturing issues resolved and get airplanes to people who want to buy them (anyone try to buy a LSA in the last 12 months?).
What they will struggle with are the inherent limitations of the LSA class. Cessna has indicated that the airplane's structure will be aluminum unless absolutely necessary. This may be good for longevity and ease of repair but will cost weight. Consider that the venerable 150/152, very much a LSA-type performer, had MGTWs around 1600lb.
The other issue is making it easy to fly. There has been a lot of discussion about other LSA being more challenging, particularly those that aim towards speed. Cessna has a history of stable (boring?) airplanes and this will likely transfer over to the LSA.
It certainly adds credibility to the LSA idea, that's for sure.