Unless the fees increase dramatically(or the block rewards is halved a couple of times), this would hold true.
Luckily both of those are solvable problems. Block rewards will (eventually) be a tiny fraction of current value. Fees will need to rise.
Personally I would make a larger minimum fee change to the protocol. Note free transactions would still be possible but 1 satoshi fee wouldn't be valid.
Then if say 50% of miners said they won't include free transactions then people would have a choice. Send it free and wait 20 minutes or send it with a small (but above protocol enforced minimum) and wait 10 minutes. If the minimum fee (remember free is still possible) was 0.01 BTC then a block with 200 paying transactions would be worth 2 BTC. When block reward drops to 25 BTC you are looking at an 8% loss (vs 0.3% now) by not including tx fees.
There is the economic incentive to build more complex software and include paying transactions.
Currently there is absolutely no economic reason to include transactions. None. The sub fractional pennies it is worth doesn't even come close to the work, software, bugs, glitches, additional long polls, etc. Most miners just include tx to be "nice" and provide "free support" to the network they want to see flourish. As the network grows that kind of model will become more antiquated.
Note: this could also be accomplished without a protocol change by a cartel of miners with enough combined hashing power to affect transaction times. The issue there is cheating (just like in OPEC). If you draw the line at 0.01 and there are enough 0.001 to 0.0008 BTC tx there is an incentive to "cheat". Still it could be done.