A lengthy promo video for the LG G3 S (Beat) contains a spoiler for what's to come from the G3 family. The LG G3 Stylus is yet to be announced but as its name suggests it intends to tackle the Samsung Galaxy Note phablets (the Note 4 will be unveiled in a month).
The stylus sheathes into the upper left corner of the back of LG's unofficial phablet, unlike the add-on stylus of the squarish LG Vu phablets.

LG G3 family portrait • the stylus sheaths in the upper left corner
The LG G3 Stylus appears to be the same size or slightly bigger than the regular G3 and its 5.5" screen. The Galaxy Note 3 has a 5.7" screen so it doesn’t take much for a G3 version to match it in size, the Note 4 may even step down to 5.5".
Anyway, here's the video – it's quite long so you can just skip ahead to 2:40 to view the unofficial phablet.



LG G3 Beat : Product Movie