The 1070 Ti is essentially the effortless answer to Vega 56. In every other market Nvidia is pretty much dominating so they don't really have to do anything other than thank miners for taking out the only market which offered competition. AMD practically gave Nvidia a vacation since Nvidia literally has no reason to rush Volta now.
As for whether you should buy now or wait, where do you fall in the budget to enthusiast spectrum? Are you able to afford luxuries as they release or do you hold on to a more modest build for a couple years before you upgrade because wife or life priorities?