Without any 4K channels, is there any use with a Tata Sky 4K set top box?

Currently, there isn’t any use. But hope to get more and more 4K content in near future.

If you can spend those extra bucks to buy a 4K TV in anticipation of future, then why not invest for 4K Set Top Box[1] as well.

For non-4K TV sets, there isn’t any requirement at all.