I am very excited with the Growth of Tandem. Each quarter as it releases its corporate earnings statement, in my opinion, this is a growing company with a very bright future.
If a much larger corporation is more comfortable for you then certainly Medtronic may fit your criteria.
However as Johnson & Johnson (ie - Animas) has so clearly demonstrated, the size along of a company may not necessarily indicate their future intentions. That being said, there is absolutely no indication of Medtronic leaving the pump market.
Everybody must decide for themselves what is in their own best interest.