An important point that’s easy to overlook in the message indicating that U.S. intelligence believes Russian forces are suffering from shortages of fuel and other materiel — U.S. intelligence also believes that Russia has now sent in over 80% of the forces it had arrayed for this invasion. As far as waves of attack goes, this is it.
Russia could always raise more troops from elsewhere. However, those forces could take time to assemble and prepare, or the risk going into Ukraine even worse organized than the current mess.
If Ukraine can hold off the forces currently making a drive on Kyiv and other cities, they may earn themselves a much-needed breather, if nothing else. And every day that passes is a day when Vladimir Putin could go on a long vacation.