Doesn't matter; software changes rapidly and you shouldn't get married to any one implementation (or stock in a promising new sector).
By all means, upgrade the protocol, even to the Litecoin or Monero protocol or whatever. But to change
ledgers every time you need to upgrade the protocol doesn't make sense at all.
People don't want to have to play stock trader with their bank account. Fortunately, because of spinoffs (and maybe sidechains), the Bitcoin ledger is a safe place to store value even if the Bitcoin
protocol gets superseded.
The problem with this reasoning is that
Bitcoin is not a bank account. A chart was recently posted that showed Bitcoin price volatility to be in line with several other asset classes (for some relatively short historical period). Unfortunately, the asset classes were stocks, oil, and a couple of severely damaged/broken currencies. Those are all highly speculative assets.
The nature of speculative assets is that there are more than one of them, people
do play stock trader with them, and some of them fail and are replaced by others.
As long as Bitcoin is in the speculative asset category, it doesn't constitute a "global ledger" of anything akin to bank accounts and
it makes perfect sense for one speculative asset to potentially be replaced by others. That is nothing like people playing stock trader with their bank accounts.
Only when Bitcoin achieves the status of a reference currency can it claim legitimacy as a ledger that is (even somewhat) immune from the nature of speculative winners and losers, not before.