I have to be honest and say it's far from certain. You can see signs that appeal of the longer format is weakening in all but England and Australia. Players feigning injury, lack of motivation (they would rather be at the IPL to pick up a hefty paycheck). And to be honest, even in England the test game ( as far as attendance is concerned) is only very well supported against Australia. If the Indians living in the UK did not attend the series against India then those grounds would be half empty. I think it is only the Ashes and maybe South Africa series they can sell out.