A prediction of Apple losing its dominance "over a couple of decades" is useless. It's almost guaranteed to occur at some point by statistics alone, in exactly the same way as any single wine glass in a restaurant will eventually be dropped. Plus reversion to the mean, obviously.
And the fate of Samsung, (and some other company I can't even remember but that was dominant for Android phones before that) shows that the Innovator's Dilemma just doesn't apply, at least not yet. The theory's whole stick is that it describes a mechanism that cannot be defended. That's why it's termed a "dilemma". Apple has successfully withstood dozens of attacks with low-end generics, showing quite clearly that this is currently just a regular market.
Samsung and other competitors also show that it's ridiculous to analyse this market in time frames of "decades". At that resolution, it's quite likely that, when the history of this market is eventually written, Samsung wouldn't even show up! The rather wild swings in profits and market share of all competitors also show that for the market segment in general, a single year (which not coincidently aligns with the product cycle) is the adequate granularity. It's only Apple that somehow manages to show a rather strange stability among this volatility.