Point of sale software is a mature and fragmented market. While there is a clear shift to mobile POS, the unique needs of different types of retailers will prevent any one player from being dominant. Over time all these players will need to focus on their competitive advantages - so Square will be compelling for micromerchants, Knome for heavy Groupon users, Lightspeed Cloud for bike stores, Revel for quick service restaurants, MicroBiz for small multi-channel retailers, Shopkeep for small stores/cafes, etc. There are too many different workflows for different types of retailers - so I do not see anyone being 'dominant' across all retail segments.