This map shows the planned improvements to the interstate system along the corridors 51 and 88. Solid blue lines indicate primary options for ultimate interstate corridors. Dotted blue lines indicate optional alignments and corridors. Thick red lined indicate existing interstate routes. thin red lines are existing freeways and loops. Several options are listed below for ultimate interstate corridor 51 including an eastern route that bypasses the city altogether. Current plans seem to have I-51 routing along US-281 (IA-29) to to Mason City rather than Minneapolis through Rochester, MN as recommended here.

Ultimate Interstate 251 - Downtown connector
Description Ultimate interstate 251 would replace the short segment of I-380 heading into downtown Waterloo from US-20 (ultimate I-51 and I-88) it would then be extended continuing north along US-218 to its northern terminus at planned ultimate interstate 51.
Purpose and Need Since it makes more sense for ultimate interstate 51 to bypassdowntown and use SR-29 to the west instead ultimate interstate 251 would be a logical inclusion into the interstate system.