The powers that be are planning, with some seriousness, a monorail for Colombo. We saw this video which shows how awesome a monorail would be, though we don't know the source of the video. All that has been released
on the subject is that Sri Lanka is likely
to build a $1.3 billion USD (Rs. 169 billion) monorail with Japanese funding (in the initial stages). It is also estimated that the project would take eight years total (three for planning, five for construction.
If We Did Have A Monorail
If Colombo did have a monorail, the route would look something like this, with the Malabe to Fort corridor opening first. This would drastically speed up the commute from Battaramulla and the easter suburbs, of course after construction would have made commuting hell for five years (at least) in the process.
Afterwards they envision other routes connecting Colombo North and eventually a rail connection to the Airport.
There are, however, other unsubstantiated plans
circulating that show a Moratuwa to Fort line being built first.
What Would A Monorail Mean
Civilized public transit would be amazing and is, ultimately, necessary for Colombo to be an international city. However, building a monorail could be prone to cost overruns and delays and could turn out to be a huge burden on tax-payers.
The general idea of getting into town fast, reliably and without traffic, however, is very appealing. The actual feasibility analysis still has to be done.