think about it if you were a miner, and have learnt that you can charge XXX for transaction why would you be happy to again charge just one X?
It is certain the more popular coins will increase costs to catch up with bitcoin, as opposed to bitcoin lowering .
Developers are already being pressured to behave in ways that I dare not repeat.
Generaly, I think that BTC's mining has not been as profitable as it used to be. And I agree that transaction fees are unlikely to start decreasing (or at least not drastically). And in general, this will pretty much prevent the idea of BTC becoming a paying currency.