So four "new" QTs joining JOTA with two provisionally based at SEN and two elsewhere seems to be the current consensus.
And just for completeness I repeat this from the SEN thread:
JOTA CEO Andy Green quoted in Airliner World magazine April 2017: "The company is negotiating to acquire a pair of dedicated 146QT freighters which will offer a significant increase in capacity and capability without breaking the bank. ......diversifying into the jet cargo sector waters down our market risk. If the ACMI sector dries up we won't have all our eggs in one basket. We have canvassed a lot of potential customers and there is plenty of interest. We see a need to support not only other carriers but also postal and courier contracts. The QT plugs the gap between ATR/ATP and 737 freighters. Jota's expansion is driven entirely by market demand. We have no real thoughts about whether we're going to get two aircraft or ten. There is plenty of availability in the second-hand market so we don't have to panic when it comes to acquisitions."