No-one's saying Pioneer is going away, even if the company decides to pull the plug on its TV business, which it's saying is only one of several options under consideration. A decision may be announced on Thursday, when it gives its Q3 FY09 results, or it could wait until the end of the month.
So I am sure if you have a Pioneer warranty it will continue to be honoured, and like any responsible manufacturer the company will provide spares back-up for a good while to come.
If you have a third-party warranty, then it should be entirely unaffected by any decision Pioneer may make.