In AXI4, if the length of the write burst is always equal to 0 (one transfer in burst), The wlast Signal can always be asserted in this case? If not, what should be the value of the WLAST SIGNAL?
It would always be high when WVALID is asserted in this scenario. When WVALID is de-asserted we don't care what value WLAST takes.
So you could simply always drive WLAST high if you knew all write transactions would have length 1 transfer.