On W6 page they say that Bucharest and Budapest will get a 9th aircraft (so I assumed there are 8 at the moment):
https://wizzair.com/en-GB/about_us/news/wizzen280
https://wizzair.com/en-GB/about_us/news/wizzen274
5th aircraft for Warsaw will come 29th March
https://wizzair.com/en-GB/about_us/news/wizzen274