Whether short lived files get written to the disk or not depends not only on default behavior of the kernel file cache, but also on details of file system driver implementation and mount options of the said file system. It is possible to configure the system in such a way that everything will always be immediately written down to disk (essentially, DOS-like behavior).
One file system, prominently featuring the behavior you're interested in (so called "delayed allocation") is XFS. With it you can be more or less sure (given no funny configuration options elsewhere) that blocks belonging to just deleted files will be reused in memory, without intermediate disk access. XFS may still want to update its metadata journal (which will be written to disk rather frequently; yet, given that XFS' journal is metadata only, it is small enough to be set on some other, fast device, such as battery backed RAM found on many RAID controllers).
Because of this behavior, it is not uncommon to find completely zeroed out, but otherwise legit looking files (size and other metadata intact) on an XFS file system after a sudden power interruption. Such is a cost of supporting fast "semi-temporary" file operations.
In general, a system call accessing a file system ends, rather quickly, in the file system driver defined method (attached to "struct inode_operations" and "struct file_operations" when VFS driver is registered). What happens after that is left solely to discretion of the file system implementation. Typically, something resembling the following approach is used (this simple example is from linux FAT driver):
If file system is mounted in "sync" mode, all changes go to disk immediately (through fat_sync_inode() in this case). Otherwise, the block is marked as "dirty" and stays in the memory cache until flushed at some reasonable opportunity.
Thus, it is impossible to predict the system behavior in respect to transient files without considering file system mount options and inspecting the source code of its implementation (this, of course, mostly applies to all kinds of exotic file systems mostly found in embedded space).