Is current waveform of given dc-dc converter correct?
The mistake you have made is that you have assumed that the peak current will rise linearly with time (at the end of each charging cycle) and for all time. It won't because of the load resistor; it ultimately limits the current to a maximum value: -
$$I_{0(pk)} = \dfrac{V_S}{R_{LOAD}}$$
You physically cannot get a load current higher than the above.