Ric_Tan - You're getting more than 550-600 shots (no flash or video) with your SX40's Li-Ion? Canon claims 400 for the SX40, no flash/video, and if you only use the viewfinder, not the LCD.
My 550-600 comparison is SX10 (same vintage as the SX1) - using sets of AA Eneloops properly slow-charged.
Maybe you were able to buy an after-market Super Li-Ion that's more efficient than 4 x AA Eneloops...?
Perhaps Canon will "do a Pentax K-R" for the SX50 - that is, offer the camera with a wimpy little Li-Ion - but also offer an optional holder for 4 x AAs (a lot more shots per charge) - that fits into the power-pack slot. That also gives the option - on a trip, maybe - of using 4 x Energizer Lithiums - over 1,100 shots with that camera.
The SXxx cameras are about the size of the Pentax K-R - and like the earlier Pentaxes - K200D, K-M, K-X - were formerly AA-powered.
Perhaps Canon might not make vast profits from a 4 x AAs holder for the SX50 - with the Pentax K-R, the Brand-Name holders are over AUD$60.00 (in Sydney - half that in the US) - but the option is so hugely popular, that very rapidly, third-party holders were available at rather more "sensible" prices.....
But even if Canon didn't make much selling Brand-Name AA-holders - they do make profits selling cameras - in Australia 'enormous profits'
(the SX40 is AUD$519.00 here - you can have a G12 for $50.00 more...) - and nowadays - when the SX40 is Mini-Li-Ion powered - that the Panny FZ150 is also Li-Ion is no dis-incentive over the Canon...
And (with add-on for $180.00) - the 1,020mm optical reach of the FZ150 is a bit more than the FX40's 840mm... (People tend to buy bridge-zooms for the zoom... )
- Of course - the SX50 - with 40x-plus Zoom - 1,000mm equiv, 3-level stabilisation - WITH 4 x AAs holder option - and "puh-lease" price it under $500.00 in Australia - might be even more attractive....