It is very early to comment about possibility of Ubuntu to overtake Android or iOs.
But the Mobile manufacturers like BQ "AQUARIUS E4.5 " is being launched with Linux Ubuntu.
The comments of the users seems to be promising.
Here are the specs.
IPS multi touch screen, 5 capacitive points,. Protective Dragnontrail display
qHD 540 x 960 - 240 ppi, Aspect ration 16:9; Viewing angle 178 o
Quad Core Cortex A7 up to 1.3 GHz MediaTek
Mali 400 up to 500 MHz
Internal memory 8GB, RAM 1 GB
LiPo 2150 mAh
Dual micro SIM
3.5 mm headphone jack
Micro-USB OTG slot
MicroSD slot, up to 32 GB
3G HSPA+ (900/2100)
2G GSM (850/900/1800/1900)
Wi-Fi 802.11 b/g/n
GPS and A-GP
OS : Ubuntu
Rear 8 Mpx (Dual flash and autofocus) Aperture f/2.4
Front 5 Mpx