If Bitcoin were to hit some limit, I dunno what, just maybe there is a limit in the code which people might start writing threads about on bct, but anyway, if Bitcoin hit some limit and couldn't scale anymore, then the network effect is arrested. Bitcoin, just being software that can be copied does not have the privilege of gold which is a rare physical element.
In fact it does have the "privilege of gold".
There are plenty of other metals that are as scarce as gold (such as platinum). There are also plenty other earthly materials which are as scarce.
Scarcity is essential but it isn't everything. "Everything" is network effect. Network effect is far harder to attain than anything else. For evidence of that check http://www.coinwarz.com/cryptocurrency
The network hashrate (in other words, "interest in mining the coin" of bitcoin is 364 Peta hashes). The nearest altcoin in terms of hashrate is Mazacoin at 80 Terra hashes.
So, for the purposes of this example, lets use hashrate to test your theory that
So, if Bitcoin hit some limit and couldn't scale anymore, then the network effect is arrested
...and that that concept affects its value:
Ergo, your "theory"is complete B.S. because Bitcoin hit all sorts of limits ages ago - not anonymous, not fast enough, slow confirmations, huge blockchain - and yet, still no altcoin can get near it in terms of market cap or hashpower.
Meanwhile the only reason Bitcoin still "has" that value is because it is the cryptocurrency reserve and there are altcoins "out there" which solve all Bitcoin's technical problems.
Umm... Mazacoin is nowhere near second place in terms of hashrate among the SHA-256 coins. Heck, it probably isn't even in the top 5. The reason why MZC is second place in that list is because Peercoin and Namecoin's hashrates are shown as "?". If you look at BitInfoCharts, you can see that Peercoin's current network hashrate is 150 TH/s and Namecoin's is 100 PH/s.
EDIT: Merged mining probably explains why Namecoin's hashrate is so high so Peercoin would be the closest "true" competitor.