He seems to be the best WK option currently for ODIs if we take into account other options. The only other middle order WK batsmen who has impressed in recent times in List A cricket is Mohammad Haris who is still developing. Rohail has been struggling to create impact and is not in best of the forms since a season or two. Sarfaraz is 35, yes he plays spin well and next WC is in India but is he the answer? Something to think about if Riz is not able to make impact in ODIs before the WC. Azam Khan's fitness needs improvement and needs to play some big knocks as he has decent game against spin which is important for middle order position of no 4-5 but, currently not an option. Zeehsan Ashraf, Bismillah and Mohammad Akhlaq prefer top order positions while Haseebullah is still very young and is also a top order batsman.
Rizwan has been outstanding in the other two formats so deserves an extended run. However, I believe he needs to improve his game (SR) against spin by increasing the range of strokes he has to tackle spin. I think this has been the key difference for Rizwan while batting at no 4 in ODIs vs opening in T20Is, he is not that comfortable starting against spin (Its different when you are facing spin with new ball that mainly skids).