That's a removable artificial limit, not a hard one.
By tweaking some settings, the network could easily be scaled to many times that.
If it ever became an issue (read: the network started to consistently max out the TPS limit), the ceiling would be lifted. If that wasn't sufficient, effort would be put into making the network more efficient. If that wasn't enough, more creative solutions would come into play (offline transaction systems, systems built to manage BTC outside of the blockchain [see CoinKite], etc).
