Even if you have high confidence the stock market will swoon in the near future (I'll leave the market timing debate to others), I think you should at least keep maxing the 401ks for the tax benefits, even if you don't want to invest the contributions in the short term.
I am guessing that you are not in a low tax bracket, since you would be able to pay off a 60k mortgage in 10 months. In that situation, the tax benefits to the 401k contribution almost certainly are much greater than your mortgage interest rate (maybe something like 25% in tax deferred savings versus ~4% mortgage interest rate?). This depends to some degree on your particulars (when will you start drawing from retirement savings, what is your likely interest rate at that time, what is your mortgage rate, etc.), but I doubt it is a close call.
If you are really confident a market correction is impending, you could just shift your new 401k contributions into a money market fund or some low volatility option for a time. A secondary consideration is that you only get so much space each year to shovel money into accounts that can grow tax free. That space is valuable, especially if you won't make withdrawals for a while.
Even if you decide to stop putting money into retirement accounts for a bit, the second question is whether paying down the rental mortgage is the best use of that cash flow. I understand the psychological security of owning property free and clear, but that doesn't mean its the most economically rational decision. There is a pretty good argument that a reasonable amount of low-interest mortgage debt is good debt:
-The mortgage interest is deductible against the rental income. That's a remarkable government subsidy of your mortgage.
-A low-interest mortgage is a good inflation hedge. Failing another housing market collapse, I look forward to paying the 2017 mortgage on my rental property in 2027 dollars I receive from my 2027 rental rate.
The question is , does it make more sense to save for a downpayment on another rental property or make some other non-stock market investment (any other debt?) rather than pour everything into this one mortgage?