Mid-June is an odd time of year. Apple's hardware refresh cycle isn't really due until October -- likely six full months away -- so you might consider picking up an external battery pack to use with your current iOS device to tide you over until then.
Internal batteries drop in efficiency as devices age, and replacement prices can be a little steep. An out of warranty iPhone or iPad battery replacement can cost upwards of $85 or $105 with shipping.
If you're a developer, this goes double. With iOS beta season under way, mobile devices are eating up batteries in new and curious ways. This isn't uncommon, as early releases of operating systems often contain debugging processes that are removed before the system goes "gold".
External battery units are becoming more affordable than ever and newer systems like the Antec PowerUp 6000 support recharging both iPhones and iPads with high-amperage USB ports. I've been using an Antec review unit for the last couple of weeks and have found it a solid performer for light-weight emergency power.
The Antec is a portable pack that fits nicely into a pocket. Its design has soft edges, easy port access and a built-in indicator light. You charge it using USB (rather than, say, plugging directly into a wall socket). I've tested it with iPhones, iPads, and a variety of other USB-powered devices including the Kindle Fire and Bluetooth speakers.
It's a bit hard to fully review the Antec PowerUp external battery ($60 MSRP, $42 street price) as Amazon customer criticisms of the product center on its losing its mojo after a few months of continuous use. My work style doesn't include long periods of off-grid demands, I haven't regularly drained the unit, and I've been pretty faithful about plugging it in at nights.
A spokesperson from Antec promised to get back to us with a statement about these issues. We'll add an update when he does so. Because of these issues, TUAW does not feel comfortable recommending or not recommending the product based on our testing.