Buybacks usually mean the company thinks their stock is underpriced. However, x86 is currently being disrupted by ARM, and the prognosis does not look good. For example, they've finally got their power consumption to around ARM levels, but the entire mobile industry is based on ARM - ARM is now the incumbent. Is this Intel hubris, or do they know something we don't?
It's honestly not clear that the underlying CPU architecture really matters anymore. Smaller customers might care about the technical hassles involved with switching to a new architecture, but smaller customers don't count. The larger customers care much more about per-unit cost savings, and not at all about NRE costs. In any case there isn't a lot of ARM assembly out there these days, and everything else can retarge…
It seems to me that Intel has traditionally benefited from the fact that CPU architecture has mattered (in x86's favor). The mere fact that x86 is no longer the only sensible choice, while obviously not a doom prophecy for Intel, isn't really an argument for Intel's continued relevance.