Accuracy of sakura predictions

How accurate are the sakura predictions?

Is it too late to book a hotel now for tokyo, Osaka, kyoto during sakura season (I can't afford too expensive prices)

Thanks

Not very accurate, especially so early during the season. Usually it is the temperatures of early to mid March that have the biggest influence on the timing, and humans simply cannot accurately predict the temperatures over more than a week or so.

Here is a page by Weathermap that analysis their forecast of the previous year:
https://sakura.weathermap.jp/result2017.php

Also, if it rains or if there's strong winds, a lot of blossoms will fall off the trees. Then they're pretty bare for a while until late bloomers appear. Traveling to see the cherry blossoms is always a gamble, but it's incredible if you manage it.