The father-to-be tweeted early this morning, thanking the former Pussycat Doll for her work on the show.
"Nicole will always be a part of the X factor family. Now signed to Sony as an artist. Thank you Nicole for everything."
He also teased rumours that Cheryl Cole will be returning to the show, hinting that he had some very "exciting news" to share with everyone soon…
In a string of posts about this year's series of The X Factor UK, Simon also explained his decision to return to the panel:
"The last time I appeared on X Factor UK it resulted in over 45 million record sales.
"So I decided last year to return home to the UK show."
He added: "And to anyone considering applying for X factor this year. Do it. We are taking this year very seriously. It's all about the talent."
The new judging line-up is heavily rumoured to include former mentor Cheryl Cole, Louis Walsh and Dannii Minogue, in a return to the favourite 2009 format.
And Cheryl has done little to deny the rumours, posting a picture of her and Simon on the show on her Instagram account as part of #TBT (throwback Thursdays).
We can't wait for Simon Cowell to dish out that exciting X Factor news already!
Who would you like to see on the judging panel for The X Factor 2014? Let us know in the Comments Box below now.