OTL, the population of Hungary without Croatia and the Banates was around 4,5 million in 1500. The Hungarians comprised around 70% of this population. Add Croatia and the Banates to the equation it would be around 5 million, 5,5 million if we're optimistic. In 1700, the entire population of the Danubian Habsburg realms was roughly 9 million. Given the 200 years difference, I believe these numbers are easily comparable.
If the country's borders remain intact, with only the Southern border regions experiencing frequent raids, the population could easily grow to 9 million and past by 1700. Not only the population would be higher, but without the devastation of the wars in the core territories, the country would be significantly richer as well. The reemergence of the precious metal mining would give a significant boost to the wealth of the country through the XVIIIth century, which would allow investments into projects like regulating the major rivers and making them navigable, building roads or even constructing canals. This would boost trade and allow formerly flooded areas to be populated, while canals could improve agricultural productivity. As the country becomes wealthier, expansion becomes feasible as well. Venetian Dalmatia would be conquered sometimes in the 1700s and Ragusa could be integrated not so long after. The struggle with the Ottomans for the dominance over the Romanian principalities would also restart around this time. By the end of the XVIIIth century, making territorial gains against the Turks could also become possible.
Hungary( including Croatia the Banates and aforementioned gains) reaching a population of 20 million by the beginning of the 19th century could easily be the case. Assuming the technology of the world being consistent with OTL, the industrial revolution could reach Hungary by the 1820s. Through the century wars with the Turks could be fought, and depending on the circumstances regarding Poland and Russia, Hungary might establish dominance over Wallachia, Moldavia, and most of the Balkans. Eventually, during the second part of the century, this could lead to the establishment to a federation of the crownlands of the Holy Crown.
This new entity would be populous, industrialised and strong militarily, and would eventually pass France in every relevant aspects. The official name could be "Lands of the Holy Crown", but could be simply referred to as Danubia or something. Maybe the England-Austria Effect would kick in, and people would refer to the whole entity simply as Hungary.