Hi speed burts: I use a lot of Hi continuous shootins sequence with my K-7. Possibly 1/3rd of my shots are in Hi continuous mode. I never had any major problems, beyond my own mistakes.
I cannot comment directly on other camera bodies, but I read very few reports (in PF) of problems/incidents with other Pentax dSLRs with Hi continuous shooting
Wildlife photograhy: IMHO any camera body will do the job because the ost important component is the lens. Go to the Pentax Lens discussion in the PF and you will find there several threads on wildlife shooting. Your selection of lenses will be the key decision to ensure good shots.
Hope that the comments will help...