1999-2007 - Applied biosystem ( now Lifetech) was the leader using 3700 and 3730 sequencers.
2006-2010 - Roche gained almost 80% of market.
2008-2012 - Illumina short read tech gained momentum with GAII, Hiseq and Miseq. Miseq will still be workhorse for sequencing in future for Reference based applications.
2011-ongoing - Lifetech SOLID ( not used widely in market), IonTorrent and IonPhoton are very popular for short reads sequencing but has very limited applications, also error rate is very high. IonTorrent is in direct competition with Miseq and is already one of market leader.
2012-ongoing - Pacbio is gaining ground with ultra long reads and Pacbio will dominate denovo and DNA base modification studies, Long reads will also help identify large rearrangement which were not possible before.
2013 will the year of Pacbio as they focus on sales of second generation Pacbio sequencer, I think Roche (or someone) might buy Pacbio which has Market cap of 200M (looks cheap)