Members have reported that they have received letters from the DWP, but if you consider the hundreds of thousands that have to be sent, they will not all arrive at the same time. So you cannot read anything into the fact you have not received one.
BIS
Nothing on this board constitutes legal advice - always consult a professional about specific problems
Strange you should mention this, for the previous 2 years I have had my DLA annual letter stating my benefit amount on 8th February each year. I had my DLA-PIP f2f in December, and still awaiting a decision, and have not had my usual benefit amount annual letter yet.