More than 30% roi before even adding gen2 to the hashrate seems like a decent investment to me.
That's assuming they can keep paying the same dividends weekly for two years. That is a highly speculative position: they might take a two year hiatus to develop the next gen of chips (the saved coins) and have negligible mining revenue. Still, might strike "gold" though.
Do you assume it takes them 2 years to bring the next generation online? Or are we talking about another, future, generation?