I love Rugby! And I have begun to love Cricket. However, I wouldn't be very excited to see these two disciplines at the Olympics. Both Cricket and Rugby have a very, very long tradition, which was created without the Olympic Games.
Let's think about rugby: the great tradition of rugby was built through the 4-5-6 Nations Championships, through tthe test matches against New Zealand, South Africa or Australia, through the British Lions, through the Barbarians and since 1987 through the World Cup. I think that cricket is more or less similar: the Ashes, the test matches played in India, Pakistan, the West Indies... and the World Cup. What would the Olympic Games add to these two wonderful games? I would say nothing.
Rugby: first of all, it is impossible to play a long tournament in just 15-20 days. Rugby is such an exhausting game that you need at least 4-5 days of rest! Then, let's imagine rugby at the Olympics: no England, no Scotland, no Wales, no Ireland, but United Kingdom and the Republic of Ireland. Irish team would not represent both Eire and Ulster, but only Eire, which is a terrible strike to rugby traditions.
I have heard that Rugby Sevens could be added to the Olympic Games, but I am not so excited about it.