Absolutely, but only those houses that have kept the faith – the Freys were always uncertain in their loyalties (look how they bolted from Whitewalls and managed to get away clean) and now they’re joined at the hip to the Lannisters. The Yronwoods fought in three separate rebellions, so I think their loyalties are rock-solid.
Keep in mind, the number of Blackfyre loyalists has been on the decline in the long run – they had half the kingdom in the 1st Rebellion, but the 2nd Rebellion was limited to the hardcore and even then a lot of former Blackfyre supporters wisely stayed away. The 3rd Rebellion seems to have been the highwater mark – much of the realm was deeply alienated from King Aerys’ neglect and Bloodraven’s police state, and Bittersteel was able to land in force and wage a full-scale war with multiple battles. He even had enough supporters at court to help him escape after his capture.
Likewise, Aenys Blackfyre must have had some base of support to even contemplate making the trip to Westeros, and Bloodraven wouldn’t have had him killed if there wasn’t a significant group of Blackfyre loyalists who needed to be threatened into obedience.
However, the 4th Rebellion showed far less support on the mainland. When the Golden Company landed on Massey’s Hook, only a few lords rose with them and they were easily bottled up on the peninsula and badly beaten at Wendwater Bridge. By the time that Maelys the Monstrous attempted his invasion of the Stepstones, his only support came from Essos.
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