For I know what has gone by, but I do not know what is to come: Good News Bible provides a good model for this verse. The following model of Contemporary English Version is also helpful:

• I know how long we’ve waited in the past, but I don’t know about the future.”

Quoted with permission from Bullard, Roger A. and Hatton, Howard A. A Handbook on 1-2 Esdras. (UBS Helps for Translators). Miami: UBS, 2019. For this and other handbooks for translators see here.