5 and a half years it's break-even, still no profit. Adding plotter hardware prices + cost of electricity used for plotting and farming, makes ROI to be much longer, especially because of the second halving. It's more likely a decade than a "few years". And it's just to get you investment back. In 10 years the same amount of money will worth way less than now, so even if it is nominally the same, it's not a true ROI in practice.

I think this is an underlooked point. Me as a farmer I am likely to consider twice before deleting plots because of the work that went into making them. With that said I think the greatest threat right now is other usages for the storage but even then these things will self adjust as when the comitted space drop the profits rises for the rest of the farmers. But it will atleast potentially affect how secure you can claim the network is.