When you buy gold you do not pay a constant tax to the miners after initial purchase.
Yes you do, every ounce they mine devalues your holding. ... under your apparent definition of tax.
could be true but that inflation of gold is way lower - low enough to not be felt. Bitcoin is a different story.
Only because gold has been mined for centuries. When the second ounce of gold was pulled from the ground, the annualized inflation rate was astronomical!
A currency can't already exist without first coming into existence. The annualized inflation rate (what you seem to want to call a "tax) of bitcoin is quickly dropping. By late 2016 it will be less than 4.25% Four years after that it will be 1.79%. Within a decade it will drop to less than 0.9%
costs for mining still have to be paid. It can't hold the value now so it won't be worth much, much more later.
So once the inflation fades out you have the choice of either make fees higher or let hashrate drop out. But because it wasn't able to hold value for decades it will not be worth a lot after these decades of inflation so i basically expect it to fiddle out or become very expensive to use.
Bottom line:
Mining hashpower needs to be paid
Right now there's much more hash than it would need and that's paid now and will be paid later too. These effects of this current bearmarket will be felt long time.
I wouldn't be so 100% sure the next bubble will arrive soon. Why should it? Buy Litecoin for 1$ next week... and the week after that for 50 cents.
There's too much hash on it that wants to be paid. Bitcoin heavily favour miners with the excuse of the security. But that security problem arises later again - meanwhile you have a bad image and a bad reputation for being unable to maintain a value.
This problems indentified here will not just vanish into thin air with a halving.
hashrate = expenseswhat i say is: either hash comes down or expenses go up
It's very unfortunate Bitcoin
can't hold its value now and is not attractive to invest into, for that reason.
(until it's not) 
