Not that I have any in mind right now, except perhaps
.....
Doesn't seem to make sense for them to take it away??
You answer the question in the second part with the statement in the first part. Apple explicitly addressed it when introduced the laptops last year. Apple said their marketing info was that there was less than 1% of the users using the slot. In other words, the vast majority of folks never leave that initial state you stated you were in. "maybe I'll use it" or "it nice to have because eventually" or "it makes it more future proof" or etc. etc. etc.
ExpressCard's come in two flavors. Cards which are really just USB connections and those that utilize the PCIe bus. Again in broad range of situations where the card is really a USB card with a funky connector you can find a mainstream USB equivalent. ( Unless had maxed out the USB and/or firewire bus the other sockets also provide solutions. ). Similarly, for stuff like CF cards there are FW solutions with similar speeds. (only a problem is doing saturated I/O on multiple fronts. )
The physical socket for the ExpressCard also takes up more internal room and more complicated connection ( since have to hook it into two different buses). For the cards with PCIe interfaces need drivers which leads to support complexities. So the slot is not a top 10 on the design priority list.
Usually there is a wave of folks saying "well I use a XXX card" so there much be thousands of users. The problem is that is not normalized over the number of MBP sold. If 40,000 express card users and 3,000,000 units then that is slightly over 1%, but be for real. That means 98.7% of the users aren't using it.
Additionally, Apple said was that there was a higher percentage of folks who made a disproportionate share of impact up in the 17" class of machines. For example if, 20,000 ECard users and 300,000 17" units then up in the 6% range. Still not in the double digits but snagged a significantly higher percentage of the usage. Additionally, there is significantly more room in the 17" so not a matter of squeezing something else out. That number would only get higher if more of the 40,000 "move up" to the 17" over time. Once 10% or 25% of 17" users are using ExpressCard then as long as 17" stays around much easier to use this platform to deliver on.
Lots of folks claim that Apple can't count and their knowledge of what people have installed in their computers is much deeper and pervasive than Apple's. I have yet to find any of those accounts very creditable.
Post widespread USB 3.0 deployment, ExpressCard is likely doomed to legacy equipment anyway. It is a "dead slot walking" format. There are going to be devices sold, but the units sold are going to go down hill going for here forward. USB 3.0 has practically the same bandwidth profile with default plug-n-play support in the standard.
In contrast, the vast majority of MBP owners own a SD card. Whether buried in a cellphone or camera the coverage rate of who could use a SD slot is significantly higher. It is focused on what people already have, not on what they "could buy maybe in the future". That's the key difference.
Likewise, Apple's rationale on dumping FW from 13 was flawed; new camera have USB connectors. The number of new cameras with FW is dropping ( USB is pervasive and at this year's CES 2010 almost exclusive even in Prosumer HD camcorders). However, the number of deployed and in use cameras with FW is still huge. Likewise completely overlooks the number of FW hard drives deployed in the mac market also (and how much USB 2.0 sucks relative to FW800 in real bandwidth). FW is even more present on Windows PC hardware now than ever before although stuck at 400. It was premature and short sighted to drop FW while still significantly utilized.
The stated rationale is illustrative of what drives Apple. If a slot/connector is "obsolete" and there is a new substitute then Apple will dump it rather than carrying it several generations. ExpressCard is a bit premature in getting dumped. Squeezed out more so because other elements in the MBP 13" and 15" had higher priority on space in addtion to be "more problematical" than alternatives.