Seriously though, with all due respect (and with admittance of my conflict of interest here) - alt-coins (or rather, truly innovative alt-coins as opposed to one-two tweak clones) are useful.
They prevent monoculture.
If anything, we need more altcoins pursuing different niches (I feel that there are market niches which BTC, contrary to popular belief, fills imperfectly, allowing for an alt to take that niche without affecting mainstream btc adoption - but that's a long and boring story)
Arguably, what you want is one timestamping chain. All other chains can then use that timestamp service to establish ordering of their transactions.
That is effectively what merged mining actually does anyway.
It would allow the main chain headers to be extremely clean.