Rate hikes won't do much and endless printing doesn't affect the short term value of the dollar. As long as international investors are confident in the US economic model, they will continue to invest in the US markets (the recent rise in the markets can be attributed more to European angst than a "Trump rally".)
The challenge to the US dollar will come in the next crisis. With the advent of cryptocurrencies and many other nations coming together for trade without the use of the US dollar, the challenge to the US dollar is dependent on the next crisis. The crisis has to be large enough with concerning magnitude that it forces investors to seek safety in other tangible assets and not the US dollar. Then we'll begin to see the demise of the dollar. But this is not an overnight event. Lets not forget that a "collapse" in the US economic confidence model also means a renewed world war and this time it will be kinetic and not a cold war.