SRA has seen phenomenal growth over the last 6 years. Total number of submissions went up from 7240 in August to 10193 today. That is a gain of 40%. The number of transcriptome-related entries went up from 1078 to 1643 (52% gain).
Here are the quarterly breakdowns of SRA submissions as it stands today. The first chart shows all submissions including genomic and transcriptomic experiments, whereas the second chart shows only transcriptome-related submissions. The exponential trend observed before Q4 2010 did not come back after 2010.