when you can apply for citizenship depends on how long your wife has been in the uk and what type of visa she came to the uk on.
but for most on here who came to the uk on a spouse visa, its 3 years. after 2 years in the uk on a spouse visa she should have got ILR, and 1 year after that then she can apply for citizenship.
ILR could be scrapped in the future, 60% of those who have ILR go on to apply for citizenship, the gov want the other 40% to decide. if they do this whats the point of ILR ? or only give you ILR for a set time period, who knows what their plans are. but there are 100,000s on ILR here.