I'd actually like them to keep their independent engine in all honesty and have them not transition to webkit/chromium nor any other. The reason is selfish, not because I use their products for daily browsing, but because as a webmaster it allows me a verification of my crafted things after validation against the standards; in 3 different standards compliant engines: gecko, webkit and opera after which I feel confident enough that I can say I've done my part and now the "trident" based crappy browsers (IE) need to adapt to the standards (or well I'll have to add stuff to work around their bugs and other mistakes).
Loosing one of those independent standards compliant implementations is a bad thing in my book. A pity.
Mobile: it's all already webkit anyway (safari and chrome), the rest doesn't get used in my stats.