I don't know 3DR's future plans myself, but it's no secret from various sources on the Internet, that Qualcomm is a large investor in 3DR, Qualcomm have their own hardware called the Snapdragon Flight, which it has to be said is very good.
Whilst the Arducopter software is very powerful and well supported by a community, the fact it's open source means that 3DR has put its money into supporting the software, meanwhile cloners build Pixhawk compatible hardware without contributing back with hardware improvements or contributing to Arducopter.
So it looks like 3DR is moving to PX4 so that 3DR will no longer have to share its code. With that 3DR would lose one of the benefits of Solo with future products, as long as 3DR keep their great customer service and allow users to still extract and examine their own log files, then I'm not too worried, if they simply become another DJI though that would worry me.
For Solo owners there's no real issue as Solo's code is becoming part of the main branch of Arducopter so you'll get new firmware for many years to come. Also as the Pixhawk 2 is being sold seperate and will have companion computer options there's a possibility you'll be able to upgrade your Solo yourself in future.