Spark switches over to Tailwind?

"Licenses are valid for an entire major release "series". In other words, a license entitles you to all updates until the next series release. That current series is Spark Aurelius (initially released February 2018) and includes Spark 6.0+. New series are released roughly once every two years. Many minor updates are made throughout a series release and all of those updates are free to existing customers. Each license may only be used on a single site unless it is an "unlimited" license."

-- https://spark.laravel.com/licenses

However, upgrading from an old license (v5 in my case) is only $49 (vs $99):

"This will upgrade your license to the latest version of Spark, granting you access to its source code. License upgrades are offered at a 50% discount to existing Spark customers."

So if I buy the software now. I won't get any updates in 1-2 months. This is bad

If you're buying now, you're buying a certain version of Spark. That version will be updated at long as it's supported. It's based on Laravel 6, which is a long term support (LTS) version.

When the next version comes out, you upgrade for half the price. Or you can just continue to use the one you bought as long there are updates for it. Laravel 6 is supported until 3rd September 2022.