No. If I run as a Republican and lose in a primary then switch to the Libertarian party I'll be viewed as someone who chooses my affiliation based on ambition rather than principle. Which would almost certainly guarantee me a lost race. I will run as a Libertarian (assuming they endorse me, which it sounds like they will) and fight harder than any other candidate for the seat.
A lot of the ideals between both parties are similar, but Libertarians believe in more personal freedoms than the Republican platform accounts for generally. Also, the Republican party has a pretty sour name this time around, especially once McCain gets the nomination.
The Republican party, as said elsewhere on this forum, is a sinking ship. They've lost their way and it is essentially beyond repair. In the midst of a presidential year election, which will always have the highest voter turn out, is not the time to be the "newer better Republican" candidate.