You waited less than an hour, chill.
Calling the Boshin War a proper war is a little bit misleading. In a lot of ways, it was sort of the post-shogunate cleanup, given that Yoshinobu had already resigned the position of shogun before the war began (though I do think it was necessary to clean out the malignant hold that the Tokugawas had over the Imperial government). However, I do think it's possible for the Tokugawas to hold off their defeat, at least temporarily. What's really important is that Yoshinobu doesn't lose his nerve at the Battle of Toba-Fushimi because of imperial support of Satsuma and Choshu, and presses the attack. If he had done this, I think he could have pulled off a (Pyrrhic) victory, due to the sheer numerical disparity, although his enemies had a better-trained and modernized army. However, this would have cost immense casualties and most likely led to sort of a truce/cold war between the Tokugawas and the Imperial government. I tend to believe that this would lead to a vast loss of political prestige and thus power for the Tokugawas, as they're directly going against imperial authority, and they will have lost many experienced warriors. In the end, by the point the Boshin War came around, Tokugawa power in Japan already had its days numbered. The only change this creates is that it stays that end for a few years at most.