The Host Card Emulation (HCE) and now launched/supported by Visa and Mastercard will be a challenge for hardware based solutions (eg. SIM, MicroSD and special memory in phone). Will be interesting to see when/how tech providers like Gemalto, G & D and Oberthur and solutions like Isis and MCX will react on this.
Still there is one point using a solution where the card info is stored on special hardware in the phone, you can pay even though the phone is off for example if battery is dead or if offline (valid for amounts up to €20/$20/£20).
MasterCard and Visa are supporting HCE for mobile payments