Almost zero. The party may still be, but the administration almost certainly won't.
Currently there is no "Republican party" just Trump loyalists. In 2030 the party might still be called the same but I doubt it will have moved far from the principles of today.
The Republican party looks about the same as it has my whole adult life -- the leader is a lot louder and the racism is less hidden, that's about it.
I don’t know how old you are but the GOP has 180’d on trade, international relations, unions, Social Security, and Medicare among many other issues over the past 30 years.
What are the odds of this regime ceding power willingly in 2028?