Against a 20-year time horizon, current prices of indexes are certainly at a discount. Just not perhaps the biggest discount we'll get this year.
Continuing to contribute in order to dollar cost average is still a smart play, although I typically would never recommend contributing to a 401k beyond what is required to get the maximum employer match, but that's me. I loathe both the way that 401ks typically work (significantly higher fees that chew up profits) and for the restricted nature of what you can invest in.
The employer match is free money. Beyond that I would fill in the IRA contribution, which is infinitely more flexible in how it can be invested. And beyond that I would just save it and eat the taxes as I went (which provides the best mix of flexibility and liquidity).